The present invention relates to apparatus and system for determining the integrity of sealed containers. The invention has particular application to parenteral pharmaceutical products which are typically packaged in rigid glass containers sealed with a combination rubber and metal closure.
Such pharmaceutical products are usually packaged by high speed automatic filling and capping equipment. The containers or bottles are filled with the medicament at a filling station and thereafter the closure assembly consisting generally of a resilient sealing element made of rubber and a cup-like cap made of aluminum is placed over the discharge end of the container. The capping apparatus then acts to apply a predetermined force to the cap to seat the closure assembly and to crimp the lower edge of the skirt of the cap under or around the bottle finish or flange to seal the container. More specifically during the capping operation the resilient sealing element is compressed between the end face of the container and the cap and held in a compressed state by crimping the cap to the container. The integrity and adequacy of the seal is, therefore, primarily a function of the percent compression of the sealing element or expressed another way, the magnitude of the seating force of the seal against the container around the periphery of the opening in the container. Proper sealing for medicaments is important to prevent exposure to air or loss by evaporation and also to protect the contents from microbiological or other contamination.
It has been found that some containers packaged by mass production techniques are not adequately sealed. The seal is controlled primarily by the capping equipment. For example, for a given cap, resilient sealing element and container assembly, the bottle-raising means of the capping equipment is initially set to apply a predetermined force to effect a given compression of the resilient sealing element to produce the proper seal. If the initial setting of the capping machine is incorrect, the seal produced is inadequate. For example, if the pre-load force in the bottle-raising means is too low, the resilient sealing element is not compressed sufficiently to seal and if too high there is the danger of metal seal distortion, dimpling of the top surface of the resilient sealing element or glass breakage. Even if the initial setting of the capping equipment is correct, the setting may require adjustment by the operator from time to time and if these changes are inadvertently overlooked, inadequate sealing may result.
Presently there are various systems for checking the seal integrity. A common system is one wherein the seal integrity is first checked visually and then usually checked further by selecting containers periodically from the assembly line and inspecting them manually by turning the cap relative to the container. If the cap does not rotate under the manual force applied, the seal was considered adequate. Such a method is clearly inherently imprecise and subjective since it depends on the strength and judgment of the tester, which may vary from person to person and day to day.
In accordance with another system for checking seal integrity which is the subject of a pending application, Rohde, Ser. No. 090,527, APPARATUS, METHOD AND SYSTEM FOR DETERMINING THE INTEGRITY OF SEALED CONTAINERS, filed Nov. 2, 1979, owned by the assignee of the present invention and incorporated herein by reference, means is provided for measuring the pre-seal and post-seal height of the container-closure assembly to determine thickness dimension change of the resilient sealing element and in turn the percent compression of the resilient sealing element (percent R.E.C.) can then be calculated. For any given combination of container, closure and other known elements, a range of percent R.E.C. can be determined which provides seals of adequate integrity as determined by other standard tests. The apparatus for determining the axial compression of the resilient sealing element and thus percent R.E.C. includes a test stand with a planar base on which the container rests, a vertical adjustment column and an indicator gauge actuated by a sensing head for detecting the pre-seal and post-seal height of the container-closure assembly. The gauge may have either a graduated dial scale for comparing pre-seal and post-seal readings or an indicated area of acceptable predetermined compression value relative to an indicated pre-seal "zero" position indicating a seal of adequate integrity. While this system is generally effective for the purposes intended, the system depends on both pre-seal and post-seal readings. Additionally, there is an inherent relaxation of the residual static force in the compressed rubber element with time due to cold flow which the displacement measuring system cannot detect.